1. Technical Field
The invention relates to local area networks. More particularly, the invention relates to a personal virtual bridged local area network.
2. Description of the Prior Art
An access point (AP) is a link-layer bridge between one or more stations (STAs) and a distribution system (DS). See IEEE 802.11, Wireless LAN Medium Access Control and Physical Layer Specifications, ISO/IEC 8802-11:1999(E), ANSI/IEEE Std 802.11, 1999 Edition. An example of a DS is a LAN segment, or an intranet. An AP enables packets to be transmitted via radio either from a station (STA) to the DS, or from the DS to a STA. An access point therefore has at least two physical ports. One is the DS interface and the other is a radio interface. Multiple STAs, each with their own radio interface, can send packets to the DS by multiplexing the single shared radio interface of an AP. The radio interface operates at a particular frequency and the STAs share the medium through a MAC-PHY protocol that guarantees mutually exclusive access to the medium. The DS also sends packets to STAs by using the same protocol.
The STA of an AP has a Basic Service Set ID (BSSID). It serves to partition 802.11 Basic Service Sets logically. Every STA that associates with an AP shares the AP's BSSID. A frame destined for a group address received by an AP or a STA is discarded if the BSS to which the AP or STA belong does not match the BSSID of the frame. In this sense, the BSSID behaves as a Virtual LAN ID (VID). See IEEE 802.1Q, IEEE Standards for Local and Metropolitan Area Networks: Virtual Bridged Local Area Networks, IEEE Std 802.1Q-1998. Every STA is therefore a member of the same virtual LAN (VLAN) as a consequence of associating with the same AP.
Every STA in a BSS, however, should not share the same VLAN unless the STAs trust each other. Yet in public space deployments, all STAs associated with an AP are required to share the same VLAN when typically there is no trust among them. This can make a STA vulnerable, for instance, to various link-layer attacks launched by an untrusted STA, such as Address Resolution Protocol (ARP) cache re-mapping.
It would be advantageous to provide a mechanism for segregating traffic amongst STAs that are associated with a bridge such that, for example, an untrusted STA associated with said bridge can not be used to launch a link layer (OSI Layer 2) attack on another STA associated with the same bridge.